Electrostatographic printers are known in which a single color toner image is electrostatically formed on photoreceptive image bearing member. The toner image is transferred to a receiving substrate, typically paper or other print receiving materials. The toner image is subsequently fused to the substrate.
In other electrostatographic printers a plurality of dry toner imaging systems, one image bearing member is used to develop multiple color toner images. Each color toner image is electrostatically transferred in layers from the image bearing members and registered to an intermediate transfer member. The composite toner image is electrostatically transferred to the final substrate. Such systems that use electrostatic transfer to transfer the composite toner image from the intermediate to the final substrate and then subsequently fix the image on the substrate in a fusing system have transfer limitations. For example, there are limitations due to stresses introduced with rougher paper stock, foils, paper moisture content variations, etc. Also, the need to electrostatically transfer a full layered color composite toner image to the substrate creates additional high stresses for electrostatic transfer. Stressful system conditions can include for example systems that may wish to use papers allowed to condition at wide ranges of relative humidity, and systems that may wish to image onto a large range of paper widths. Such stresses can have significant effect on transfer due to the effect on the electrostatic fields used in electrostatic transfer, and they can also have significant effect on paper transport. In addition with direct to paper transfer, fibers, talc and other particulate or chemical contaminants can readily directly transfer from the paper to the imaging modules during direct contact in the electrostatic transfer zones. This can tend to contaminate the imaging drums, development systems, cleaner systems, etc., and can lead to early failure of the imaging systems. This is especially true for certain stressful paper types including for example certain types of recycled papers. Due to all these and other problems, systems that use direct transfer to the final media generally have narrow media latitude for obtaining and/or for maintaining high print quality.
Alternatively, a toner image is formed on a photoreceptor. The toner image is transferred to a single transfer member. The transfer member generally simultaneously transfers and fuses the toner image to a substrate. The use of a single transfer member can result in transfer of background toner on the photoreceptor to the substrate due to the material of the transfuse member. In addition, the photoreceptor can be contaminated by heat and oil on the transfuse member from the transfuse nip.
To overcome some of the deficiencies of the single transfer, prior systems have employed two transfer belts. Toner images are formed on photoreceptors and transferred to a first transfer belt. The toner image is subsequently transferred to a second transfer member. The second transfer member is cooled below the glass transition temperature of the toner prior to the transfer nip with the first transfer belt. Cooling of the second transfer belt requires the second transfer member to be relatively thin. A thin second transfer belt however has low conformance therefore providing reduced transfer efficiency in the transfuse nip. The reduced conformance also increases the potential for glossing of the toner image in the transfuse nip. In addition, a thin second transfer belt can have a reduced operational life.